A disk drive, such as a magnetic disk drive, comprises a magnetic disk, spindle motor, magnetic head, and carriage assembly. The magnetic disk is disposed in a case. The spindle motor supports and rotates the magnetic disk. The magnetic head reads data from and writes data to the magnetic disk. The carriage assembly supports the magnetic head for movement relative to the magnetic disk. A head section of the magnetic head comprises a recording head for writing and a reproduction head for reading.
Magnetic heads for perpendicular magnetic recording have recently been proposed in order to increase the recording density and capacity of a magnetic disk drive or reduce its size. In one such magnetic head, a recording head comprises a main pole configured to produce a perpendicular magnetic field, trailing shield, and coil. The trailing shield is located on the trailing side of the main pole with a write gap therebetween. The coil serves to pass magnetic flux through the main pole.
To improve the recording density, a high-frequency magnetic field assisted recording head is proposed, in which a spin-torque oscillator for use as a high-frequency oscillator is disposed between the main pole and trailing shield such that a high-frequency magnetic field from the oscillator is applied to a magnetic recording layer. Drive current is supplied to the high-frequency oscillator, and magnetization of a generating layer is generated with sufficient amplitude. In this way, a large high-frequency magnetic field can be produced such that a stable recording/reproduction characteristic can be achieved.
To achieve a higher recording density and more stable recording/reproduction characteristic, it is necessary to apply the high-frequency magnetic field to a smaller region and obtain a greater high-frequency magnetic field intensity. A higher drive current is required for this purpose. If the drive current is increased, however, the high-frequency oscillator is gradually degraded, so that it may become difficult to achieve a stable recording/reproduction characteristic, in some cases.